1. School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2050, United States
2. Birck Nanotechnology Research Center, Purdue University, West Lafayette, Indiana 47907-2050, United States
3. Nanovis, West Lafayette, Indiana 47906-1075, United States
4. School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States